The invention pertains to the field of navigation and relates to a flight management functionality relating especially to a flight management system of FMS type. This system allows flight planning, management and prediction in both the horizontal and vertical plane. In particular, the invention targets the flight predictions associated with constraints. A constraint is an input of the pilot or of the air traffic controller (typically the altitude, the speed, a time, etc. at a point of the flight plan) that the aircraft must comply with. Constraints serve especially within the framework of air traffic regulation for civil aircraft.